Bearing



May 19, 1942. w. E. MCCULLOUGH BEARING Filed Dec. 5, 19 38 3n en or mum51M: JULLBEH I f I I (Ittomegs Patented May 1%, i942 nane BEWQ WilliiarnE. Mcmiiiough, Detroit, Mich, assignor to Eohn diuniinmn it Brass@orporation, like trait, Mich, a corporation o2 Ii iichigan Applicationhamm r is, iris, geriai No. assess (ei. sea-=23?) i illiairnsa Thisinvention relates to an improved bearing.

An object of the invention is to provide bearings of great durabilitythat will stand up under extreme conditions of abuse, such as inadequatelubrication.

In carrying out the invention a bearing formed of an alloy whichincludes lead as a major component is first given a smooth finishedsurface by machining or any other suitable finishing operation, and athin layer of lead is then electrolytically deposited on the smoothfinished surface. This thin layer of lead is of high purity, is unbrokenby seams or jointsand is firmly bonded to the underlying alloy.

These and other objects and advantages of the invention will becomeapparent as the description proceeds.

While preferred methods of carrying out the process are disclosed hereinfor purposes of illustration, it should be understood that variouschanges may be made without departing from tions, but the presentinvention insures an output of improved bearings having uniformly longlife as well as the ability to survive under extreme conditions ofimproper lubrication.

In carrying out the invention the bearing is first lined, and its innersurface is next given by machining, or any othersuitable process, asmooth, highly accurate surface conforming in shape to the shaft surfacebut with a slightly increased clearance allowing for the film of lead,which is then electrolytically deposited on the finished surface of thebearing alloy. The thickness of the lead film, which is usually aboutone thousandth of an inch (0.001) is regulated so as to just take up theclearance that was provided for it.

In the example illustrated in the drawing, a

' body it of lead-containing bearing alloy has been the spirit of theinvention as herein set forth and claimed. The process of manufacturingthe bearings is claimed in a divisional application, Serial No. 292,638,filed August 30, 1939.

In the drawing:

Fig. 1 is a perspective view of an interchangeable bearing embodying thepresent invention.

Fig. 2 is a fragmentary longitudinal section of the bearing shown inFig. l in combination with a shaft.

Fig. 3 is a reproduction of a photomicrograph showing on a greatlyenlarged scale the structure of a partial section of a bearing taken onthe same lineas'Flg. 2.

Fig. 4 is a view similar to Fig. 3 but showing .the structure when adifierent material is used and at a higher magnification.

In manufacturing interchangeable bearings such as are used in automobileand aircraft engines, it is well-known practice to provide a backing ofsome relatively rigid material, such as steel, and to line the backingwith a bearing material, such as the alloys of copper and lead, known inthe art as leaded-bronzesfl. In my copending application Serial No.231,101, filed September 22, 1938, I have described a bearing in which abacking formed of a copper-nickel alloy, such as that sold under thetrade-name Monel metal, is lined with a bearing alloy comprising silverand lead. The present invention may be used with either of these typesof bearings.

'The lead alloys of both copper and silver give quite satisfactoryservice under ordinary condl- 55 mass w h formed, preferably by aspinning operation, on the inside of the shell ii, steps being taken toinsure a'strong bond between the bearing alloy l0 and the shell H. Thesebearings are usually formed in cylindrical or semi-cylindrical shape,and after they have been suitably rough finlshed the surface of thebearing alloy which is designed to carry the load is machined to asmooth accurate surface, in this case to a cylindrical contour and witha diameter large enough to allow for the subsequent addition of a filmof lead. I

The bearing is then subjected to an electrolytic treatment suitable fordepositing on the smooth prepared surface of the bearing alloy a thinfilm of pure lead, preferably not over 0.001 of an inch in thickness.The conditions of the electrolysis can be accurately controlled toproduce a film of lead of thickness predetermined to exactly compensatefor, the excess clearance left when finishing the surface of the body80. The lead film is illustrated on an exaggerated scale at i2 in thedrawing. Fig. 3 is a reproduction of a photomicrograph taken at amagnification of-50X of part of the section of Fig. 2, and illustratesthe structure of of electrolytic a bearing in which a thin film l2 leadis deposited on a layer 10 of a silver-lead bearing alloy. In this viewthe dark areas 13 are the lead component of the silver-lead alloy, andthe figure shows clearly that wherever the lead areas of the bearingalloy were exposed at the plating surface the plated lead united withthe lead component of the alloy to form a homogenous lead mass. As thelead molecules are deposited they unite to form a molecularly continuoussurface, and they also form a molecularly continuous lead portions ofthe bearing alloy.

again it is evident that the electrolytic lead has united homogeneouslywith lead portions 83 of the copper-lead alloy. Satisfactory bearingsmay be made from copper-lead alloys containing from 15 to 50% of lead.

Fig. 2 illustrates a typical relation of bearing to shaft according tothis invention for aircraft motors. In such motors a typical bearing ofaverage size is at present designed to have a clearance of threethousandths (0.003) of an inch on a side, which clearance is shown at itbetween the bearing and the shaft l5. The film of electrolytic lead,shown at If, is approximately one thousandth (0.001) of an inch thick,as previously explained.

When bearings made according to this invention are .-run'in underoperating conditions in the presence of lubricating oil, they all withpractically nocxception acquire the hard, glassy surface over the entirebearing area which is the sign of a good bearing. The hard surfaceresults from the formation of a lead compound under the conditions ofoperation. The composition of this lead compound is not definitelyknown, but results prove that the presence of the thin film of pureelectrolytic lead insures the formation of this perfect surfacecondition on all bearings, whereas when the lead bearing alloys are usedwithout the electrolytic lead film a certain proportion of bearings failto acquire the desired bearing surface, and must be replaced afterrelatively short periods of service.

It has been found that bearings. thus formed are able to run forextended periods of time without showing any appreciable signs of wearon the lead film. It has also been found that such bearings are able tosurvive severe conditions of inadequate lubrication such as might resultfrom the failure of the normal oil supply. It is believed that thesesuperior operating characteristics of the improved bearing are due tothe fact that electrolytically pure lead has very good wettingcharacteristics with lubricating oil, and

hence if there is any oil at all available a com-' plete oil film ismaintained between the bearing and the shaft. Moreover even when dry,lead has a relatively low coefficient of friction with steel, of whichthe shaft is composed, and hence the bearing can carry its load for ashort period of time without critical failure after stoppage of the oilsupply.

The present invention makes it safe to use a lining of pure, soft lead,because the thin film of lead lies over a finished surface of theunderlying alloy, which surface is of itself sufficiently ance, and theengine would be able to continue functioning until a repair station isreached.

While the invention has been illustrated as applied to cylindricalbearings having bearing metal composed of silver-lead or copper-leadalloys, it should be understood that any variation of these alloys orany suitable bearing alloy containing lead may be used as a base for theelectrolytic lead film. And'it should also be understood. it can beapplied to any lead-containing bearing regardless of its shape, and thatthe improved bearings can be used in a wide variety of devices.

I claim:

1. In a bearing of the type having a layer of lead overlying a layer oflead-containing bearing alloy, the improvement which comprises: afinished bearing surface on the bearing alloy; and a thin film ofelectrolytic lead of uniform thickness covering the finished surface ofthe bearing alloy, said-lead film having a molecularly continuoussurface and being molecularly continuous with lead portions of thebearing alloy.

2. In a bearing of the type having a layer of lead overlying a layer ofcopper-lead bearing alloy, the improvement which comprises: a finishedbearing surface on the copper-lead bearing alloy; and a thin film ofelectrolytic lead of uniform thickness covering the finished surface ofthe bearing alloy, said lead film having a molecu- -larly continuoussurface and being molecularly continuous with lead portions of thebearing alloy.

3. A bearing comprising: a layer of silver-lead bearing alloy having afinished surface; and a thin film of electrolytic lead of uniformthickness covering the finished surface of the bearing alloy, said leadfilm having a molecularly continuous surface and being molecularlycontinuous with lead portions of the bearing alloy..

4. In a combined structure in which a bearing surrounds a shaft, thebearing comprising a layer of lead overlying a layer oflead-containing'bearing alloy, the improvement which comprises: afinished bearing surface on the'bearing alloy conforming in contour withthe shaft and of such size as to have a normal clearance plus a slightadditional clearance; and a thin film of electrolytic lead of uniformthickness covering the finished surface of the bearing alloy and fillingsaid additional clearance, the lead film having a molecularly continuoussurface and be- V ing molecularly continuous with lead portions ofsmooth to serve as a relatively eflicient bearingsurface. Furthermorethe thickness of the lead film is only a fraction of the normalclearance (one-third in the example illustrated in Fig. 2) between shaftand bearing. Hence should any extreme conditions develop under which thefilm of lead is squeezed or worn from the bearing, the underlyingbearing. surface could assume the load without a detrimental increase inbearing clearthe bearing alloy and constituting a smooth surface withoutthe necessity of any machining operation prior to installation.

5. In a combined structure in which a bearing surrounds a shaft, thebearing comprising a layer of lead overlying, a layer of lead-containingbearing alloy, the improvement which comprises: a finished bearingsurface on the bearing alloy conforming in contour with the shaft and ofsuch size as to have a normal clearance plus an additional clearanceapproximately one-third the size of the normal clearance; and a thinfilm of electrolytic lead of a uniform thickness equal to the size ofsaid additional clearance, the lead film having a molecularly continuoussurface and being molecularly continuous with lead portions of thebearing alloy and constituting a smooth surface without the necessity ofany machining operation prior to installation.

6. In a combined structure in which a bearing surrounds a shaft, thebearing comprising a layer of lead overlying a layer of copper-leadbearing alloy, the improvement which comprises: a finished bearingsurface on the bearing alloy con- 7 forming in contour with the shaftand of such size as to have a normal clearance plus a slight additionalclearance; and a thin fllm of electrolytic lead of uniform thicknesscovering the finished surface of the bearing alloy and filling saidadditional clearance, the lead film having a molecularly continuoussurface and being molecularly continuous with lead portions of the Aalloy and constituting a smooth surface with ut the necessity of anymachining operation prior to installation.

7. In a combined structure in which a bearing surrounds a shaft, thebearing comprising a layer 15' of lead overlying a layer of silver-leadbearing alloy, the improvement which comprises: a finished bearingsurface on the bearing alloy conforming in contour with the shaft and ofsuch size as to have a normal clearance plus a slight additionalclearance; and a thin film of electrolytic lead of uniform thicknesscovering the finished surface of the bearing alloy and filling saidadditional clearance, the lead film having a molecularly continuoussurface and being molecularly continuous with lead portions of thebearing'alloy and constituting a smooth surface without the necessity ofany machining operation prior to installation.

E. MCCUILOUGH.

